Will Frost Kill Freshly Cut Grass?

You don’t often see any lawn mowing going on during the winter months, especially during the heart of winter. There’s a reason for that, and it has little to do with preference. As beautiful as that first early morning frost is, it can damage your grass.

Layers of frost essentially freeze your grass, and since grass halts its growth cycle in the winter, mowing it can cause tremendous damage because grass simply can’t recover from it. 

Lawn grass is already full of water molecules, and without any ability to generate heat, a layer of frost will quickly freeze those molecules. 

If you’ve cut your grass during a freeze, not only can it not grow and recover, it’s basically frozen in place, with expanding and contracting temperature reactions causing more damage. 

How Does Frost Affect Freshly Mown Grass?

Grass is affected in a variety of ways if it’s hit with even a moderate frost after mowing. Some of it may not die, while some of it may. 

Since it cannot heal through new growth, it is open and exposed to the outside elements. 

Freshly cut grass that is exposed to frost soon after can suffer from a variety of long-term effects:

  • Brown and/or Yellow Patches
  • Rot
  • Fungal Growth
  • Altered look come springtime
  • Remains Dormant

Brown or yellow grass will take some work to fix. First, you’ll have to remove any remaining dead grass that is no longer rooted in the ground by raking it away and disposing of it. 

Aerating the ground where you see yellow patches will help, as you will have to spread fresh grass seeds in these areas. 

Aeration will stimulate the roots and help revive some of the yellow/brown grass while paving the way for the new grass seeds.

As mentioned above, cutting the grass before a frost is subject to rot.

Rot is typically a disease that can infiltrate the grass through an open cut that couldn’t heal in the cold. 

Most likely, it will be take-all root rot or something similar, and there are various ways to treat it. 

How to Treat Grass Damaged From Frost

Fungicides are your first step, followed by regular mowing—no shorter than four inches—and plenty of water. Going through and raking out any dead grass will also aid in healing. 

But, most importantly, don’t mow your grass before a frost.

Some grass may not grow back at all once damaged by frost, and you’ll have to aerate and sow fresh seeds in the springtime. Occasionally, you’ll also find that damaged grass will never look right.

You can either leave it the way it is or pull it up and replant grass seeds. 

The damaged look is likely to remain for a long time, as the grass there is essentially stunted and too badly damaged from the frost that it won’t grow but isn’t exactly dead either. 

When Is It Appropriate To Mow The Lawn Close To Winter?

You should stay away from the lawnmower whenever it is less than 40°F outside, and you shouldn’t consider mowing over two weeks before it drops below that temperature. 

You’ll also want to wait at least two weeks after the final frost before cutting grass. 

The best way to get a good idea of when it’s time to mow is to wait until you see the grass beginning to grow again. This way, you know the grass is no longer dormant and won’t be damaged by a fresh cut.

What you’re basically looking for is a sustained temperature that is above 40°F. This is also the appropriate time to spread fertilizer. 

Over the long winter months, the grass has been dormant, and the nutrient-rich soil has lost a bit of its bounce. 

Spreading fresh fertilizer in the springtime will help your grass rebound faster, not including the regular benefits you get from a good fertilizer.

How To Take Care Of A Frozen Lawn?

First and foremost, frozen grass is just that, frozen. It snaps when it’s stepped on, even by young children who don’t weigh as much. 

Of course, it’s no different than mowing it, so you end up achieving the same result just by walking across the lawn.

Take care of your lawn during the winter by staying off of it whenever there has been a frost. However, it’s ok to walk on it during the thick of winter, so long as the temperature isn’t low enough to freeze the grass blades.

While you shouldn’t mow your lawn before a frost, that doesn’t mean you shouldn’t do anything with it. One of the best times to aerate and fertilize your lawn is when you’re closing in on that first frost. 

Consider Aerating Your Yard Before A Frost

Aeration will help provide some drainage and give the soil breathing room before your grass goes into hibernation for the winter. It’s also important because it’s an excellent excuse to rake the leaves off your lawn.

Removing excess leaves allows your lawn to breathe and provides plenty of sun and water for your grass. Fall time is also an excellent time to seed new grass for next year’s growth. 

  • Rake excess leaves away
  • Aerate and seed your lawn
  • Fertilize before the first frost
  • Minimize time on your lawn over the winter

Fertilize Your Lawn Before A Frost

You’ll want to stick with a fertilizer high in potassium and low in nitrogen for the final spread before winter. The main reason is that nitrogen puts grass into growth overdrive, something you don’t want it to do right before the first winter chill arrives.

The remaining nutrients, such as potassium, will help the grass beef itself up before it goes dormant, effectively shielding it from the worst that harsh winter conditions have to offer. 

The more robust your lawn is going in, the better off it will be coming out. 

Can You Mow Your Lawn At All During The Winter?

Yes, you can, and in fact, it’s encouraged to do so. So long as you follow the rule on a minimum temperature of 40°F, you’ll be just fine mowing your grass over the winter break. 

The only caveat is that sometimes it is difficult to tell exactly when the temperature will drop below 40°F. 

Meteorologists are paid very well for years of education followed by years of expertise, all so they can give you a wild guess about weather conditions. 

When you do mow the lawn over the winter, make sure that you do it when the grass is not wet. 

Mid-morning is always the best time during the summer, spring, and even into the fall because it’s not too hot and the morning dew has burned off. 

However, it may take a little longer for that morning dew to dissipate in the winter, so your hours may fluctuate a bit, depending on how the grass feels. What you’re looking for is dry grass and a reliable weather forecast. 

Lastly, you’ll want to raise the blades on the mower. The last thing you want to do is cut too deeply into grass over the winter. 

The more blade there is, the more sun exposure, and grass needs sun, especially in the short months of the winter season. 

Final Word

Mowing your lawn in the winter can be beneficial, but only if done correctly. First, ensure the grass is dry and the temperature is above 40°F, and raise the blades on the mower to avoid cutting too deeply into the grass.

If there’s frost on the grass, leave it alone until it melts.

With these tips in mind, you can help keep your lawn healthy all winter!

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